Project Summary/Abstract The use of psychotropic medications in women of reproductive age and in pregnant women has markedly increased in the last decade. Animal models suggest potential cognitive teratogenicity, but there is limited (mostly low quality) to no information on the risk of neurodevelopmental disorders in humans following in utero exposure to these medications. Understanding the effect of specific psychotropic medications (i.e., comparative safety), dose, and polytherapy on adverse neurodevelopmental outcomes is important for guiding the prescribing of these medications to women who are or who may become pregnant. Such information is also of crucial importance to regulatory agencies in light of the new Pregnancy and Lactation Labeling Rule. Finally, understanding the connection between in utero psychotropic exposures and neurodevelopmental disorders will allow for targeted early interventions in children at risk. Whereas certain outcomes can be (and have been) studied in the context of small prospective cohort studies, large-scale studies using existing real- world data are the only option available for evaluating the risk of more severe and clinically significant neurodevelopmental outcomes. We will address these clinical questions using pregnancy cohorts nested in two national longitudinal healthcare utilizations databases in the US, representing over 4 million publicly and privately insured pregnancies combined. Rich information on potential confounding variables and their proxies, and state-of- the-art epidemiological methods will be used to carefully control for factors such as shared home and family environment, genetic predisposition, maternal nutrition, quality of prenatal care, other pregnancy exposures, and the approach to parenting in the setting of maternal mental illness. Novel methods will be used to help determine the critical etiological window during pregnancy, which the aim of delineating periods of safe versus unsafe use. Specifically, we will examine the risk of neurodevelopmental disorders ? including autism spectrum disorder, attention deficit/hyperactivity disorder, and developmental delays ? following in utero exposure to (1) mood stabilizers and other anticonvulsant drugs, (2) antidepressants, (3) antipsychotics, (4) psychostimulants. This effort builds upon the experience of a multidisciplinary research team - a collaboration between Brigham and Women?s Hospital, the Harvard T.H. Chan School of Public Health and Brown University. The findings from this research will improve the quality of mental health care for the large number of women that struggle with mental illness during their reproductive years and during pregnancy, and as such will have a direct and large public health impact.